Process to afford gamma butyrolactone and tetrahydrofuran

Details Process to afford gamma butyrolactone and tetrahydrofuran Process to afford gamma butyrolactone and tetrahydrofuran

2001-08-01

2002-08-13

Dentz, Bernard (Department: 1625)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

C549S325000, C549S429000, C549S508000

Reexamination Certificate

active

06433193

ABSTRACT:

This application is a 371 of PCT/EP99/08536 filed Nov. 8, 1999.
The present invention relates to the production of tetrahydrofuran and gamma butyrolactone by hydrogenation of crude or refined maleic anhydride recovered from the off gases from the catalytic vapour phase oxidation of n-butane.
Due to the reduced production costs from n-butane, maleic anhydride (MAN) is a very attractive starting material for the production of derivatives like tetrahydrofuran (THF), gamma butyrolactone (GBL) and butanediol (BDO) by catalytic hydrogenation.
Several procedures have been disclosed for making GBL, THF and BDO via hydrogenation of MAN and/or carboxylic acids, expecially maleic acid. The following patents can be cited:
U.S. Pat. No.
U.S. Pat. No.
U.S. Pat. No.
5,502,217
5,473,086
4,985,572
U.S. Pat. No.
U.S. Pat. No.
U.S. Pat. No.
4,973,717
4,973,713
4,827,001
U.S. Pat. No.
U.S. Pat. No.
U.S. Pat. No.
4,810,807
4,782,167
4,772,729
U.S. Pat. No.
U.S. Pat. No.
U.S. Pat. No.
4,659,686
4,609,636
4,550,185
U.S. Pat. No.
U.S. Pat. No.
U.S. Pat. No.
4,550,150
4,155,919
4,096,156
U.S. Pat. No.
U.S. Pat. No.
3,957,827
3,370,067
JP 32,439/74
JP 43,683/69
DE 2,715,667
DE 2,605,107
DE 2,553,761
DE 2,519,817
GB 1,551,741
GB 1,534,232
FR 2,505,819
FR 2,310,331
EP 0 745 589 A1
EP 0 722 923 A3
EP 0 543 340 A1
EP 0 417 867 A1
EP 0 285 420 A1
EP 0 277 562 B1
EP 0 198 682 A2
EP 0 198 681 A2
EP 0 147 219 B1
PCT 92/02,298
Several different catalysts have been proposed for the conversion of MAN into GBL,THF and/or BDO. As taught by these patents, a performant catalytic system comprises an element of the VII B group of the Mendeleev Periodic Table, preferably Rhenium or a compound thereof, associated with at least one noble metal of group VIII, preferably Palladium or a compound thereof, on a carbon or inert oxide support.
A catalyst of this kind has been first described by GB Pat. 1,551,741 and by DE Pat. 2,519,817.
As described in the technical and patent literature, MAN is fed to the hydrogenation preferably dissolved in a solvent.
U.S. Pat. No. 4,810,807 describes a hydrogenation process wherein MAN is dissolved in n-butanol.
DE Pat. No. 2,519,817 describes a process where MAN is dissolved in dioxane.
U.S. Pat. No. 4,782,167 describes a process wherein once dissolved in water, MAN is fed to hydrogenation as a maleic acid solution.
The use of organic solvents for dissolving MAN involves complex distillation steps in order to allow recovery, purification and recycling of the solvent.
On the other hand, the use of a maleic acid solution presents the advantage of simplifying the sequence of operations in the plant where butane is used as feedstock for the production of MAN.
The integration of the maleic anhydride process with the hydrogenation process results in a simplified maleic acid recovery (as opposed to MAN) and avoids MAN purification and refining.
Feeding maleic acid has, however, a negative impact on process economics since 10 to 15 mols of water are fed to the hydrogenation reactor, for each mol of MAN.
Compared with anhydrous MAN hydrogenation, where only about one mol of water forms for each mol of MAN converted to GBL or BDO, plus one additional mol per mol of THF formed, processing the reactor effluent in the presence of a large excess of water complicates THF recovery, GBL and/or BDO purification, and water separation.
Furthermore, maleic acid hydrogenation at relatively high temperature and pressure results in a corrosive environment requiring expensive construction material.
DESCRIPTION OF THE INVENTION
Therefore, the most important aim of the present invention is that of providing an optimized process for the production of GBL and THF, based on an efficient integration between the maleic anhydride process and the hydrogenation process, wherein the problems and troubles of using an aqueous maleic acid solution are solved to a great extent in an industrially convenient manner.
According to the present invention, the above aim has been accomplished by proposing a process for the production of MAN by n-butane oxidation in the vapour phase, wherein the oxidizing medium is air or, preferably, pure oxygen (or enriched air) mixed with reaction gases, and wherein MAN is recovered from the reaction gases by using an organic solvent as absorption medium, that is a solvent which is a MAN hydrogenation product at the same time, namely GBL.
The use as a solvent of a product from the process object of the present invention avoids all the drawbacks and costs associated with the recovery and purification of an additional chemical solvent which is extraneous to the process, and further avoids the high costs arising from the use of water as solvent which is described by other patents.
A further important feature of the process object of the present invention is that MAN, and not maleic acid, is essentially the major absorption product, despite the large amount of excess water which is present in the butane oxidation effluent.
Such a thing avoids the difficulties related to corrosion and also avoids the need of any expensive construction material, as it is the case when maleic acid is subjected to hydrogenation in the presence of water.
The process object of the present invention is further characterized by comprising the following operations:
a) Converting n-butane to MAN by catalytic vapour phase oxidation.
b) Recovering MAN from the effluent gases from the butane oxidation by selective absorption into GBL, forming a MAN-GBL mixture.
c) Removing water from the MAN-GBL mixture in a stripper, under the action of a gas and/or under vacuum, producing a MAN-GBL mixture with a minimum water and maleic acid content.
d) Recovering GEL from the exhaust gases that leave the maleic anhydride absorber, by water absorption;
e) Dehydrating the GBL recovered and recycling it to the maleic anhydride absorber;
f) Hydrogenating the dewatered MAN-GBL mixture over suitable catalyst(s) under conditions that favour THF and GBL formation.
g) Separating THF, GBL and by-products from the resulting hydrogenation mixture, by distillation.
h) Recycling a GBL rich stream to the MAN selective absorption.
The main advantages of the process object of the present invention can be summarized as follows:
a) It does not use an extraneous organic product as a solvent, such as dioxane, which would be difficult to recover and purify.
b) It avoids the use of a large excess of water as in the case of the processes wherein a maleic acid solution is used, and wherein high energy consumptions are required for water separation and THF and GBL recovery.
c) It avoids to feed corrosive maleic acid to the hydrogenation reactor, which would require expensive construction material, as for instance hastelloy.
d) A non refined fraction of the GEL product is used as solvent for the maleic anhydride absorption, allowing an optimum integration of the maleic anhydride process with the hydrogenation process.
e) THF and GBL are obtained from MAN in high yields.
Assuming that MAN is produced by a total recycle, high productivity process, wherein oxygen is used as the oxidizing medium, the process object of the present invention is able to produce GEL and THF with a consuption that approaches 1 Ton of butane per Ton of GBL equivalent, with reduced investment and optimized operating costs.
DESCRIPTION OF PREFERRED EMBODIMENTS
The sequence of the operations involved in the process object of the present invention is shown in FIG.
1
.
The process of this invention is valid for any process wherein n-butane is converted to maleic anhydride by catalytic vapour phase oxidation.
The effluent gases from the maleic anhydride reactor (line 1) are conveyed to an absorber (2) where MAN is recovered by countercourrent washing with a GEL rich stream being recycled from the hydrogenation unit (line 3) and from a GBL stream recovered from the exhaust effluent gases (line 9).
In the lower section of the absorber (2), the resulting MAN-GBL mixture is contacted with a gas stream (line 4).
Under the gas and heat stripping action, most of the water countained in the MAN-GBL mixture is re

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